AURELIA AURITA 39 



considerably wider. They serve the purpose of carrying the 

 genital cells from the gonads which are situated in the gastric 

 pouches, to the stomach. On the floor of the pouches, surround- 

 ing the gonadial groove is a horseshoe-shaped genital ridge and to 

 the inside of it and closely applied to it a row of gastric filaments. 

 The system of radial canals is quite complicated and subject to 

 great variations although it follows a definite plan. One can 

 always recognize four perradial branching canals, four interradial 

 branching canals and eight adradial straight canals. The per- 

 radial canals arise from the corners of the stomach between the 

 gastric pouches and soon give off two opposite branches while 

 the main stem runs straight to the periphery and opens into the 

 circular canal near the base of the perradial rhopalium. The 

 primary branches subdivide several times and spread over the 

 space between the central branch and the adjoining adradial 

 canals. Their terminal branches open into the circular canal. 

 The interradial canals arise from the gastric pouches and branch 

 in the same manner as the perradial canals. But the primary 

 branches are formed so close to the beginning of the canal that 

 they produce the impression of two independent canals. The 

 adradial canals have no branches. They arise from the gastric 

 pouches and run straight to the periphery, opening into the 

 circular canal halfway between the rhopalia. The circular canal 

 follows the edge of the disc between every rhopalium. When it 

 reaches a rhopalium it forms a horseshoe bend around its base. 

 The cavities of all tentacles and rhopalia open also into the cir- 

 cular canal. The entire gastro- vascular system, from the edge of 

 the mouth to the last ramifications of the canals is naturally 

 lined with endoderm. The majority of the cells of which the 

 layer of endoderm is composed are cylindrical ciliated epithelial 

 cells. In the stomach are many glandular cells. In the gastric 

 filaments numerous nematocysts occur. The grooves of the 

 mouth-arms are also lined with endoderm. The labial tentacles 

 are rich in nematocysts. 



Subgenital pits. When one examines the subumbrella 



